Differential output lamp containing chlorine and hydrogen

ABSTRACT

A differential output incandescent lamp of the pulled turn coil type, having an on-off duty cycle, contains chlorine and hydrogen to establish a halogen regenerative cycle. The amount of chlorine varies between 3.6 X 10 7 and 5.1 X 1o 7 grams atoms/cc, and the amount of hydrogen varies between 1.8 to 4.0 X 10 7 gram atoms/cc.

United States Patent [191 Holcomb et al.

[11] 3,83Lfl53 Aug. 20, 1974 DIFFERENTIAL OUTPUT LAMP CONTAlNING CHLORINE AND HYDROGEN [75] lnventors: Richard H. Holcomb; Warren D.

Young, both of South Euclid, Ohio [73] Assignee: General Electric Company,

Schenectady, NY.

[22] Filed: June 28, 1973 [21] Appl. No.: 374,787

[5 7] ABSTRACT A differential output incandescent lamp of the pulled turn coil type, having an on-off duty cycle, contains [52] U.S. Cl 313/222, 313/174, 313/179, Chlorine a d hydrogen to establish a halogen regener- 313/316 ative cycle. The amount of chlorine varies between [51] Illt. Cl. H01k 5/02 36X10-4 and 5 1 1 7 grams atoms/cc, d h [58] Fleld of Search 313/174, 179, 222 amount f hydrogen varies between 1 to 4.0X10-7 gram atoms/cc. [5 6] References Cited UNITED STATES PATENTS 6 Claims, 2 Drawing Figures 3,644,772 2/1972 Yuge 313/174 l I49 2L2\ EL: 20 I? I9 1 r 7/ 1 DIFFERENTIAL OUTPUT LAMP CONTAINING CI'ILORINE AND HYDROGEN BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates generally to electric incandescent lamps. More particularly, it relates to incandescent lamps of the differential output type and the use of hydrogen and chlorine to establish a regenerative cycle to keep the bulb wall free of tungsten blackening.

2. Description of the Prior Art The elimination of bulb wall blackening has been an objective of the lamp industry over the years. Vaporized tungsten from the filament deposits on the bulb wall thereby decreasing the value of lumens per watt over the life of the lamp.

It was found that halogens, such as iodine, Fridrich et al, U.S. Pat. No. 2,883,571, bromine and chlorine, TJampens et al, U.S. Pat. No. 3,418,512, combine with the tungsten on the bulb wall to form compounds such as tungsten iodide and tungsten bromide which dissociate at the filament into free halogen and tungsten with the tungsten being redeposited on the filament. This type of tungsten-halogen cycle or reaction occurs at certain bulb wall temperatures. If the halogen gas is more reactive, such as chlorine, the bulb wall temperature required for the reaction is less than that of iodine. It was also believed that the more reactive gas would corrode lamp parts, and therefore, hydrogen should be added to the fill gas to combine with the free halogens.

Many new and different lamp types attempted to use the tungsten'halogen principle. One such application is a differential output lamp used in a photo reprographic machine to uniformly illuminate photocopy paper. These special lamps are more fully described in US. Pat. No. 3,295,007, assigned to the assignee of the present invention. 1

Because the bulb wall temperature in certain types of reprographic lamps is comparatively low in certain cations and because a lamp is cycled on and off, it is difficult to establish and maintain a tungsten-halogen cycle to keep the bulb wall clear.

Iodine has been tried in some differential output lamps and was relatively inactive in preventing bulb wall blackening over the lighted area due to vaporized tungsten deposits and the forming of tungsten-iodine deposits in the cooler non-lighted areas of the bulb wall. Bromine has also been tried and, although an improvement over iodine, deposits still formed in the cool areas and interfere with the light output from the filament.

Chlorine and hydrogen have been used in differential output lamps as is described in West German Pat. No. 1,948,481. In this instance, the ratio of hydrogen to chlorine must always be greater than 1.25 and can be as great as 2.50. It is believed that the regenerative halogen cycle would not work with these ratios presumably because this amount of excess hydrogen ties up a SUMMARY OF THE INVENTION It is therefore an object of the invention to make an effective differential output regenerative cycle lamp. A further object of the invention is to make a differential output lamp in which wall deposits are minimized or are of such a nature and so located that they absorb a minimum amount of light. Still another object of the invention is to be able to fill the lamp with a chlorine compound which is readily controllable and easy to handle in the manufacturing process.

The objects of the invention are accomplished through the use of chlorine and hydrogen as part of the great amount of chlorine and forms I-ICl thereby leavv ing an insufficient amount of chlorine to act as a regenerative cycle agent. Other chlorine-hydrogen combinations such as claimed in U.S. Pat. No. 3,644,772 are inadequate because the amount of chlorine, 2.0 l0 7 fill gas for the differential output lamp. It has been found that a fill gas containing between 3.6 l0 and 5.1 l0' gram atoms/cc of bulb volume of chlorine and between 1.8 to 4.0 1O' gram atoms/cc of bulb volume of hydrogen with the ratio of hydrogen to chlorine varying in the range between 0.352 and 1.11 will yield an improved regenerative lamp. The amount of chlorine and hydrogen indicated are effective for lamps with duty cycles having an off time of between 0 and 28 seconds.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view of the lamp of the invention; and

FIG. 2 is an enlarged fragmentary section view of a portion of the lamp shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 of the drawings, a differential output incandescent lamp 10 shown therein comprises an envelope ll of light-transmitting glass or quartz, a differential output filament l2, foils 13 and outer leads 14. The foils 13 are hermetically sealed at either end in pinch seal 15.

Lamp 10 is exhausted and filled with a fill gas containing small portions of hydrogen, chlorine and inert gas such as argon or nitrogen. After the lamp has been filled, the exhaust tube is tipped off. The tipped-off residue of the exhuast tube is shown at 16.

Differential output lamps of the invention can have numerous types of filament configurations which give more light or radiant energy at the ends than at the middle of the lamp. In the lamp illustrated in FIG. I, filament 12 has coiled portion 17 and pulled turn sections 18. Supports l9 prevent sagging of coiled section 17 and support pulled turn sections 18. As shown in greater detail in FIG. 2, pulled turn section 18 is merely one or more drawn turns of what was once a coiled section. Although a preferred embodiment is illustrated, other filament configurations using longer or shorter coiled segments and longer or shorter pulled turn segments can be used with the fill gas mixtures of the invention. Pulled turn sections 18 will conduct current,

incandesce slightly and generate heat, which is small by comparison to coiled section 17.

Differential output lamps of the prior art first used iodine to prevent envelope blackening caused by tungsten deposits on the bulb wall. Because of the temperature required for iodine and tungsten to react and in the inability of certain lamp types to attain and maintain this temperature, the area of the bulb wall 20 across from the lighted coiled portion 17 would blacken. This accumulation of tungsten would decrease the useful life of the lamp. The blackening of this type of iodine lamp is most prevalent in lamps having a long off cycle.

Lamps were then filled with bromine since the bromine-tungsten reaction temperature is less than that required for iodine and tungsten. Although bromine lamps were an improvement over iodine lamps, various yellow-red deposits of what is believed to be tungsten oxybromide formed at the ends of pulled turn sections 18 as shown at 21. The yellow-red deposits decrease with increasing distance from the end of pulled trun section 18 to the center as shown at 22. The deposits being again in the same tapered fashion as the opposite end of pulled turn section 18 is approached. Any attempt to reduce the'bromine level and, in turn, the tungsten oxybromide formation results in tungsten deposits formed across from the coiled portion 17.

In an effort to obtain an effective halogen regenerative cycle, chlorine, which reacts with tungsten at a temperature lower than that of both bromine and iodine, and hydrogen were introduced into the lamp. Apparently, because of the potential corrosive effect of chlorine on lamp parts, it was believed that an excess of hydrogen was necessary to combine with chlorine and form I-ICl. The ratio of hydrogen to chlorine in prior art lamps was in excess of 1.25. However, it is believed that for the pulled turn type lamp the regenerative cycle will not work at these ratios and the bulb wall would blacken.

After various experiments, it was found that the hydrogen-to-chlorine ratio should be 1.11 or less but equal to or greater than 0.352. Because pulled turn section 18 generates some heat, it was found that more hydrogen should be used, more hydrogen by comparison to a lamp which has short-circuited segments. Additionally, the corrosive effect on lamp parts of free chlorine at these hydrogen levels was greatly retarded.

In determining the proper amount of chlorine and hydrogen to be used in the lamp of the invention, the duration of off time of the on-off duty cycle was found to be an important factor. This is so because the bulb wall of a lamp which, for example, is off 25 seconds will be at a lower temperature than one which is off for five seconds.

Accordingly, the amount of chlorine necessary for a lamp with an off time of between and 28 seconds is between 3.6X" and 5. 1X10 gram atoms/cc of bulb volume. The amount of hydrogen can vary from 1.8 to

4.0 l0' gram atoms/cc.

The lamp of the invention is an improvement over lamps of the prior art in two ways. First, there are no deposits on the bulb wall across from the lighted coiled section 17 as shown in FIG. 2 at 20. This probably is due to the fact that the bulb wall 7 at 20 is in excess of approximately l40".

Although chlorine may be added to the lamp as an element or compound, the preferred form is as carbon tetrachloride, CC1 In one particular commerical embodiment of the lamp of the invention, it was found that 5.l l0 gram atoms/cc of chlorine and 3.3 10" gram atoms/cc of hydrogen effectively prevented blackening of the bulb wall and chlorine attack of lamp parts. This particular lamp operated on a duty cycle of 2.0 seconds on and 28.0 seconds off. In addition to these parameters, the lamp was filled at a pressure of 3.2 atmospheres and contained argon as an inert gas. This lamp generally operates at 1,000 watts and can have a voltage of or 230 volts.

What we claim as new and desire to secure by letters Patent of the United States is:

l. A halogen regenerative cycle incandescent lamp of the differential output pulled turn type, having a duty cycle with an off time within the range from 0 to 28 seconds, comprising an elongated tubular envelope, a filament of the differential output pulled turn type extending axially of said envelope, current supply conductors connected to respective ends of said filament and hermetically sealed in said envelope, a filling in said envelope of an inert fill gas, a quantity of hydrogen and a quantity of chlorine, the improvement which comprises a selection of gases wherein the chlorine is present in the range of about 2.6 l0' gram atoms/cc to 5.1 l0 gram atoms/cc, the hydrogen is present in the range of about 1.8 to 4.0X10" gram atoms/cc and the ratio of hydrogen to chlorine varies from approximately 0.352 to 1.11.

2. A halogen regenerative cycle incandescent lamp as described in claim 1 wherein said quantity of chlorine gas is equal to 5.1 l0 gram atoms/cc, said quantity of hydrogen is equal to 3.3 10 gram atoms/cc and the duty cycle is 2.0 seconds on and 28 seconds off.

3. A halogen regenerative cycle incandescent lamp as described in claim 1 wherein said chlorine is added to said lamp in the form of carbon tetrachloride.

4. A halogen regenerative cycle incandescent lamp as described in claim 1 wherein said duty cycle has an on time of two seconds and an off time of 28 seconds.

5. A halogen regenerative cycle incandescent lamp as described in claim 1 wherein said duty cycle has an on time of 2.5 seconds and an off time of 3.5 seconds.

6. A halogen regenerative cycle incandescent lamp as described in claim 1 wherein said duty cycle has an on time of 1.5 seconds and an off time of 1.0 seconds.

UNITED STATES PATENT OFFICE' CERTIFICATE OF CORRECTION Patent No. 3 831', 053 v Dated August 20, 1974 invent fl Richard H. Holcomb and Warren D. Younq It is certified that; error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In column 4', line 35, v changev "2.6" to --3.6--"

Signed and sealed this 3rd day of December 1974.

(SEAL) Attest: v V v McCOY M'. GIBSON JR. I f "c. MARSHALL DANN Arresting Officer Commissioner of Patents 

1. A halogen regenerative cycle incandescent lamp of the differential output pulled turn type, having a duty cycle with an off time within the range from 0 to 28 seconds, comprising an elongated tubular envelope, a filament of the differential output pulled turn type extending axially of said envelope, current supply conductors connected to respective ends of said filament and hermetically sealEd in said envelope, a filling in said envelope of an inert fill gas, a quantity of hydrogen and a quantity of chlorine, the improvement which comprises a selection of gases wherein the chlorine is present in the range of about 2.6 X 10 7 gram atoms/cc to 5.1 X 10 7 gram atoms/cc, the hydrogen is present in the range of about 1.8 to 4.0 X 10 7 gram atoms/cc and the ratio of hydrogen to chlorine varies from approximately 0.352 to 1.11.
 2. A halogen regenerative cycle incandescent lamp as described in claim 1 wherein said quantity of chlorine gas is equal to 5.1 X 10 7 gram atoms/cc, said quantity of hydrogen is equal to 3.3 X 10 7 gram atoms/cc and the duty cycle is 2.0 seconds on and 28 seconds off.
 3. A halogen regenerative cycle incandescent lamp as described in claim 1 wherein said chlorine is added to said lamp in the form of carbon tetrachloride.
 4. A halogen regenerative cycle incandescent lamp as described in claim 1 wherein said duty cycle has an on time of two seconds and an off time of 28 seconds.
 5. A halogen regenerative cycle incandescent lamp as described in claim 1 wherein said duty cycle has an on time of 2.5 seconds and an off time of 3.5 seconds.
 6. A halogen regenerative cycle incandescent lamp as described in claim 1 wherein said duty cycle has an on time of 1.5 seconds and an off time of 1.0 seconds. 